Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0746fig1.ps} \end{figure}$ Figure 1: HR diagram for the PNe of the sample. The $T_{{\rm eff}}$ have been derived with the Zanstra method using the helium lines (filled diamonds) and H $\beta$ line (open diamond). The hydrogen-burning post-AGB evolutionary tracks from Vassiliadis & Wood (1994) are also plotted for different core masses, indicated in the lower-right corner of the figure. In the upper-left corner the uncertainty in the luminosity due to the error of a factor two in the distance is shown.
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In the text

$\begin{figure} \par\includegraphics[width=11.2cm]{0746fig2.ps} \end{figure}$ Figure 2: SWS and LWS spectra. See Sect. 4 for details.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.2cm,clip]{0746fig3.ps} \end{figure}$ Figure 3: $G_{\rm0}$ versus diameter of the nebulae. The solid lines represent theoretical $G_{\rm0}$ at a given diameter for different luminosities and distances where a, b, c, d, e and f correspond to L/d² ratios (in W m^-2) of 100, 24, 6, 2.8, 1.2 and 0.4 respectively.
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In the text

$\begin{figure} \par\includegraphics[width=16.5cm,clip]{0746fig4.eps} \end{figure}$ Figure 4: Comparison of the atomic fine structure line fluxes and the incident flux density of the oxygen- and carbon-rich PNe with the theoretical PDR models of Kaufman et al. (1999) and W. Latter as reported in Fong et al. (2001). The error in $G_{\rm0}$ is approximately of the size of the plotted symbols. Note that the oxygen-rich PN Mz 3 is not plotted because it lies outside the model predictions for $G_{\rm0}$ . The intensities of the oxygen lines for Mz 3 (the carbon line is not observed) are also higher than those predicted by the models.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{0746fig5.ps} \end{figure}$ Figure 5: Top panel; comparison of the O-rich model by Kaufman et al. (1999) (dashed and solid lines) with the observational points (triangles). Bottom panel; same as the top panel but comparing the C-rich model of W. Latter as reported in Fong et al. (2001) with the observational points (diamonds).
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{0746fig6.ps} \end{figure}$ Figure 6: Comparison of the observed intensities with J-shock model predictions (van den Ancker 1999). Solid lines are values for constant density and dashed lines of constant velocity. On the x-axis, $\Sigma$ I is the sum of all measured lines.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{0746fig7.ps} \end{figure}$ Figure 7: Molecular hydrogen excitation diagrams for NGC 7027, Hb 5 and NGC 6302. The solid lines represent the Boltzmann distribution fits to the pure rotational lines (solid diamonds) and the dashed dot line is a fit to the vibrational lines in NGC 6302. The symbols represent the different transitions: 0-0S $\rightarrow$ filled diamonds, 1-0O $\rightarrow$ Open diamonds, 1-0Q $\rightarrow$ squares, 2-1O $\rightarrow$ circle.
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm]{0746fig8.ps} \end{figure}$ Figure 8: Comparison of H₂ column density and rotational temperature derived for NGC 7027, Hb 5 and NGC 6302 and a sample of young stellar objects from van den Ancker et al. (2000). The Helix nebula (Cox et al. 1998) is also plotted.
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In the text

$\begin{figure} \par\includegraphics[width=14.8cm]{0746fig9.ps} \end{figure}$ Figure 9: Ratio of masses plotted against the radius of the nebula. The numbers close to the symbols indicate the sources (see text for details): 1 $\rightarrow$ NGC 7027, 2 $\rightarrow$ NGC 6153, 3 $\rightarrow$ BD+30 3639, 4 $\rightarrow$ NGC 3918, 5 $\rightarrow$ Hb 5, 6 $\rightarrow$ Mz 3, 7 $\rightarrow$ K 3-17, 8 $\rightarrow$ NGC 6543, 9 $\rightarrow$ NGC 6302, f1 $\rightarrow$ IRAS 21282+5050, f2 $\rightarrow$ AFGL 618, f3 $\rightarrow$ NGC 6720, c1 $\rightarrow$ M 2-9, c2 $\rightarrow$ Hb 12, w1 $\rightarrow$ IC 4406, w2 $\rightarrow$ IC 5117, w3 $\rightarrow$ NGC 3132, w4 $\rightarrow$ NGC 6072, w5 $\rightarrow$ NGC 6781.
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In the text

$\begin{figure} \par\includegraphics[width=7.2cm,clip]{746fig10.ps} \end{figure}$ Figure 10: Sum of nebular masses versus the core mass.
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In the text

$\begin{figure} \par\includegraphics[width=11.2cm]{0746fig2.ps} \end{figure}$	Figure 2: SWS and LWS spectra. See Sect. 4 for details.
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$\begin{figure} \par\includegraphics[angle=90,width=7.2cm,clip]{0746fig3.ps} \end{figure}$	Figure 3: $G_{\rm0}$ versus diameter of the nebulae. The solid lines represent theoretical $G_{\rm0}$ at a given diameter for different luminosities and distances where a, b, c, d, e and f correspond to L/d² ratios (in W m^-2) of 100, 24, 6, 2.8, 1.2 and 0.4 respectively.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{0746fig5.ps} \end{figure}$	Figure 5: Top panel; comparison of the O-rich model by Kaufman et al. (1999) (dashed and solid lines) with the observational points (triangles). Bottom panel; same as the top panel but comparing the C-rich model of W. Latter as reported in Fong et al. (2001) with the observational points (diamonds).
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$\begin{figure} \par\includegraphics[width=7.4cm,clip]{0746fig6.ps} \end{figure}$	Figure 6: Comparison of the observed intensities with J-shock model predictions (van den Ancker 1999). Solid lines are values for constant density and dashed lines of constant velocity. On the x-axis, $\Sigma$ I is the sum of all measured lines.
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$\begin{figure} \par\includegraphics[width=6.8cm]{0746fig8.ps} \end{figure}$	Figure 8: Comparison of H₂ column density and rotational temperature derived for NGC 7027, Hb 5 and NGC 6302 and a sample of young stellar objects from van den Ancker et al. (2000). The Helix nebula (Cox et al. 1998) is also plotted.
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$\begin{figure} \par\includegraphics[width=7.2cm,clip]{746fig10.ps} \end{figure}$	Figure 10: Sum of nebular masses versus the core mass.
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